The Messenger of Allah ﷺ said, "When you lead people in prayer, keep it brief, for among you are the elderly, the weak, and the young."
حدثنا يزيد أخبرنا ابن أبي ذئب عن أبي الوليد
أن رسول الله ﷺ قال إذا أممتم فخففوا فإن فيكم الكبير والضعيف والصغير
Its chain of transmission is sahih. Bukhari and Muslim, along with the authors of the Sunan, narrated it through other routes at greater length. See al-Muntaqa: 1366. See also Bukhari 2:168 and Muslim 1:135.